diff --git a/2000/bmeyer/.gitignore b/2000/bmeyer/.gitignore index 79a0ac3fc..b6a5b0192 100644 --- a/2000/bmeyer/.gitignore +++ b/2000/bmeyer/.gitignore @@ -1 +1,2 @@ bmeyer +lavabus.glic diff --git a/2000/bmeyer/README.md b/2000/bmeyer/README.md index c7ce2be7d..5f7cb7f4e 100644 --- a/2000/bmeyer/README.md +++ b/2000/bmeyer/README.md @@ -1,11 +1,11 @@ # Best Utility - Bernd Meyer - Monash University, Melbourne, Australia - 1/832 Blackburn Rd - Clayton, VIC 3168 - Australia - http://byron.csse.monash.edu.au/ +Bernd Meyer +Monash University, Melbourne, Australia +1/832 Blackburn Rd +Clayton, VIC 3168 +Australia + ## To build: @@ -27,7 +27,7 @@ In a video window (white text on black background): ./bmeyer < michael.pgm > michael.glic ``` -Compare the michael.pgm to the screen output. +Compare the `michael.pgm` to the screen output. To test that you are compressing and decompressing the same way the author was, try: @@ -42,8 +42,8 @@ Also try in a reverse video window: ./bmeyer < michael.pgm 2>/dev/null | ./bmeyer > new.pgm ``` -Compare the michael.pgm to the screen output. Compare the new.pgm file -to the michael.pgm file. +Compare the [michael.pgm](michael.pgm) to the screen output. Compare the +`new.pgm` file to the [michael.pgm](michael.pgm) file. Create a large reverse video xterm, say 200 columns wide and try: @@ -63,7 +63,8 @@ Decompress that smaller glic-file: ./bmeyer -2 200 < lavabus.glic2 > new.pgm ``` -Compare the new.pgm file to the lavabus.pgm file by viewing them. +Compare the `new.pgm` file to the [lavabus.pgm](lavabus.pgm) file by viewing +them. ## Judges' remarks: @@ -94,25 +95,23 @@ to set your FPU to use 64 bit mode. See the extra build lines in the Makefile, and read the author's remarks below. If you cannot work out how to get into 64 bit mode, you can -try using -ffloat-store if you compile with GCC (this may have +try using `-ffloat-store` if you compile with GCC (this may have a performance penalty). The resulting binary will have a good chance to produce portable files, but due to the resulting double-rounding (first internally to 80 bit, then to 64 bit on writing the value to memory), there is a small but very real chance any given file produced might not be portable. -The makefile defaults to -O3 and no `asm()` call. +The [Makefile](Makefile) defaults to `-O3` and no `asm()` call. ## Author's remarks: -GLICBAWLS +This program is called `GLICBAWLS` -A) Function -=========== +#### Function -"GLICBAWLS" stands for: - - "Grey Level Image Compression By Adaptive Weighted Least Squares". +`GLICBAWLS` stands for "Grey Level Image Compression By Adaptive Weighted Least +Squares". And that's exactly what this program does --- feed it a .PGM file (either raw [i.e. P5] or ascii [i.e. P2]) on stdin, and it will @@ -131,7 +130,7 @@ and then ./bmeyer < michael.glic > michael.decoded.pgm ``` -As it turns out, glicbawls compresses greyscale images (or, more +As it turns out, `glicbawls` compresses greyscale images (or, more precisely, "natural" greyscale images) better than any other program I am aware of (with the exception of the not-yet-published program developed for my PhD thesis). Of course, this might take @@ -142,25 +141,25 @@ output to stderr (assuming white text on black background). If you have trouble recognizing the image, try squinting at it ;-). If you still have trouble, simply use a terminal or xterm with -more than 80 columns, and tell glicbawls about it by giving the +more than 80 columns, and tell `glicbawls` about it by giving the number of columns as an argument. For example ```sh ./bmeyer 260 lavabus.glic ``` -will allow glicbawls to use up to 260 columns, which makes things +will allow `glicbawls` to use up to 260 columns, which makes things much more recognizable. Still running out of space? Need to compress those images just a tad more? And maybe you can handle some loss due to the -compression? If so, you can use glicbawls' "near lossless" +compression? If so, you can use `glicbawls`' "near lossless" compression mode. In that mode, the decoded pixel values are -allowed to differ from tbe originals, but there is an upper limit +allowed to differ from the originals, but there is an upper limit on the magnitude of the difference. For example, if a maximum error of 2 is allowed, an original pixel value of 37 could be decoded as 35,36,37, 38 or 39. In order to use this mode, simply -give the maximum allowed error as an argument, with a dash ('-') +give the maximum allowed error as an argument, with a dash (`-`) before it. For example ```sh @@ -183,8 +182,8 @@ terminal for the progress display, and will decompress the result on such a terminal. -But wait, there is more --- you can also feed glicbawls .PPM files -(i.e. colour images), raw or ascii, your choice. Glicbawls will +But wait, there is more --- you can also feed `glicbawls` .PPM files +(i.e. colour images), raw or ascii, your choice. `Glicbawls` will compress and decompress them just fine. However, it only does "reasonably well" on them; It beats PNG easily, but there are certainly programs out there that can compress colour images @@ -192,61 +191,54 @@ considerably better. And don't even *think* about using it for so-called "artistic" images (i.e. anything that wasn't scanned from a photo or camera).... -***************************************************************** -* * -* WARNING WARNING WARNING WARNING WARNING WARNING WARNING * -* * -* * -* Glicball is rather CPU and FPU intensive. Don't * -* run it on anything slow. Things start to be * -* usable around 300+MHz, with 600+ being highly * -* desirable. * -* * -***************************************************************** +### WARNING + + +`Glicball` is rather CPU and FPU intensive. Don't run it on anything slow. +Things start to be usable around 300+MHz, with 600+ being highly desirable. -B) Compile Instructions -======================= -Unlike most compression program, glicbawls makes heavy use of +### Compile Instructions + +Unlike most compression program, `glicbawls` makes heavy use of floating point maths --- and not all FPUs are created equal. Most importantly, the x86 and 68k FPUs use 80 bit floating point formats internally, while most other processors use IEEE 64 bit formats by default. If not taken care of, this means that a -glicbawls file compressed on one CPU cannot generally be +`glicbawls` file compressed on one CPU cannot generally be decompressed on another. Fortunately, just about all current FPUs can be put into IEEE 64 bit mode (or at least something close enough for -glicbawls). Unfortunately, there is no standard way of doing +`glicbawls`). Unfortunately, there is no standard way of doing so. For this reason, the build file contains *three* compile lines; One for machines that already use 64 bit mode by default (most RISC processors), one for linux/x86 machines using libc4, libc5 or glibc2.0, and one for linux/x86 machines using glibc2.1 -(glibc2.1 no longer exports the __setfpucw function, necessitating -the use of gcc inline assembly. *Grumble*). +(glibc2.1 no longer exports the `__setfpucw()` function, necessitating +the use of gcc inline assembly. \*Grumble\*). So, if you are building on a machine that does not, by default, -use IEEE 64 bit floating point doubles, you'll have to define Y to +use IEEE 64 bit floating point doubles, you'll have to define `Y` to be a command that switches it into that mode. If you fail to do -so, your glicbawls executable will still be able to decompress its +so, your `glicbawls` executable will still be able to decompress its own compressed files, but you may be unable to exchange files with -glicbawls on other machines. +`glicbawls` on other machines. -C) Obfuscation -============== +### Obfuscation Most of the obfuscation of this program was driven by the -desperate struggle to fit all of glicbawls' features into code +desperate struggle to fit all of `glicbawls`' features into code that fits the IOCCC's size limits. All identifiers names are single-character, which was only possible by ruthless exploitation -of scope. There is a function M() that handles nearly all input +of scope. There is a function `M()` that handles nearly all input from stdin, handles all output to stdout, and also recursively calculates one of the mathematical expressions needed for error -modelling. There is a function that calculates (A^(-1)*b)*x with A -a matrix and b and x being vectors, and does so in a very +modelling. There is a function that calculates `(A^(-1)*b)*x` with `A` +being a matrix and `b` and `x` being vectors, and does so in a very efficient way --- but one would be hard pressed to find it. There is an arithmetic coder that is even less recognizable. A lot of loop variables don't get initialized, but instead the code is @@ -257,7 +249,7 @@ meaning all the time, and the differences between compressing and decompressing are handled in rather subtle ways all over the program. The string that holds the ascii values for displaying the progress image doubles as a description on how to find a pixel's -causal neighbours. And then there are a few #define's that really +causal neighbours. And then there are a few `#define`s that really are just in there to save a few characters, but as an added "benefit" make the source ever more unreadable. @@ -265,31 +257,30 @@ In short --- running it through the preprocessor and the pretty-printer will give you something that looks slightly less like line noise and slightly more like a C program, but unless you are a true wizard, it is unlikely to gain you any insights into -what is actually going on....[0] +what is actually going on....\[0\] -D) Bugs, Assumptions and TODOs -============================== +### Bugs, Assumptions and TODOs -Glicbawls assumes that characters are 8 bit wide, and that the +`Glicbawls` assumes that characters are 8 bit wide, and that the character set used is ASCII. If one of these isn't true, all hell will break loose. -The .PGM headers are not checked very thoroughly --- glicbawls +The .PGM headers are not checked very thoroughly --- `glicbawls` will happily try to encode lots of files that it shouldn't touch. The old adage of "garbage in, garbage out" holds in that -case. Furthermore, even if glicbawls detects an incorrect input, +case. Furthermore, even if `glicbawls` detects an incorrect input, it fails to provide a meaningful error message, and instead simply aborts. -When decompressing a near-losslessy encoded image, the maximum +When decompressing a near-lossless encoded image, the maximum allowed error is required as a command line parameter. This should really be saved in the compressed file! -Glicbawls relies on the decimal representation of all integers +`Glicbawls` relies on the decimal representation of all integers having less than 255 digits. While ANSI C does not guarantee this, it seems rather unlikely that anyone in the foreseeable future -would use images with 10^255 rows, columns or different levels of +would use images with `10^255` rows, columns or different levels of grey. Also, it is assumed that any integer used can be cast to a double and back without loss of precision. This limits the number of rows, columns and grey levels to 9 quintillion, which should @@ -302,14 +293,13 @@ million in a lottery. But if it happens to you, don't say I didn't warn you! Instead, go out and buy a lightning rod and a lottery ticket ;-) -At one point, a pointer to int is used as the target of a "%1[#]" +At one point, a pointer to int is used as the target of a `"%1[#]"` conversion in a scanf, which makes gcc rather unhappy, but shouldn't really cause anyone any trouble. The same goes for a couple of assignments which are used as truth values. -E) Algorithm -============ +### Algorithm An exhaustive explanation of the algorithm used would go beyond the scope of an info file, and would also be quite difficult in @@ -321,11 +311,11 @@ expected value is calculated by creating a least squares predictor of order 12 based on all of the previously encoded/decoded pixels. However, the contribution of each pixel is weighted according to its Manhattan-distance from the current pixel, -D. That weight used is pow(0.8,D). [1][2][3] +D. That weight used is `pow(0.8,D)`. \[1\] \[2\] \[3\] In a similar way, the prediction *errors* for all previous pixels -are combined --- a weighted average (with weight pow(0.7,D)) of +are combined --- a weighted average (with weight `pow(0.7,D)`) of the squares of all previous prediction errors is taken, and the square root of the (appropriately scaled) result is called sigma. @@ -343,22 +333,22 @@ arithmetic decoder provides the information which half the actual value is in. In both cases, the interval borders are adjusted accordingly, the arithmetic coder/decoder updated, and the interval halving repeated until the precise value has been -en/decoded[4]. +en/decoded\[4\]. [0] Yes, this could be seen as a challenge.... -[1] Actually, the weight is pow(0.8,D)/s, where s is the sigma +[1] Actually, the weight is `pow(0.8,D)/s`, where `s` is the sigma used for en/decoding the particular previous pixel. Dividing - by s is a rather arbitrary action justified only by the + by `s` is a rather arbitrary action justified only by the improvement in results. Mathematically, I can only justify - dividing by s^2, or not dividing at all.... + dividing by `s^2`, or not dividing at all.... [2] Obviously, these least squares predictors are not calculated from scratch for each pixel. Some clever reuse of earlier results allows O(1) calculation, rather than the - O(previous_rows*columns) this description would suggest. + `O(previous_rows*columns)` this description would suggest. [3] As anyone who has ever tried local least squares knows from bitter experience, there is a lot of numerical instability - associated with them. So glicbawls adds a bias towards an + associated with them. So `glicbawls` adds a bias towards an averaging predictor to the equation system the least squares predictor is calculated from. The weight that is given to this bias is constantly adjusted throughout coding/decoding, @@ -370,31 +360,29 @@ en/decoded[4]. iteration ends as soon as the interval is small enough to guarantee decoding within the requested maximum error. -#################################################################### -Photo Credit: +### Photo Credit: - Lavabus was taken by the judge, Landon Curt Noll. Michael was - provided by the author. Lenna is a 1972 Playboy centerfold. +[Lavabus](lavabus.pgm) was taken by the judge, Landon Curt Noll. +[Michael](michael.pgm) was provided by the author. [Lenna](lenna.glic) is a +1972 Playboy centerfold. - michael.pgm +- [michael.pgm](michael.pgm) - The author's Godchild and nephew. + The author's Godchild and nephew. - lavabus.pgm +- [lavabus.pgm](lavabus.pgm) - A bus that was trapped by lava from Kilauea volcano in - Hawaii, USA. Nobody was in the bus at the time, BTW. - Photo date: 1981. + A bus that was trapped by lava from Kilauea volcano in Hawaii, USA. Nobody + was in the bus at the time, BTW. Photo date: 1981. - lenna.glic +- [lenna.glic](lenna.glic) - A November 1972 Playboy centerfold was scanned in long ago and - has been used for image compression research since then. Playboy - originally threatened to prosecute unauthorized use, but - eventually granted that, having been in use for image compression - testing for so long, it was now a useful benchmark. (Note: This - picture doesn't show very much.) + A November 1972 Playboy centerfold was scanned in long ago and has been used + for image compression research since then. Playboy originally threatened to + prosecute unauthorized use, but eventually granted that, having been in use + for image compression testing for so long, it was now a useful benchmark. + (Note: This picture doesn't show very much.) ## Copyright and CC BY-SA 4.0 License: diff --git a/tmp/winners.csv b/tmp/winners.csv index e88294997..c08d36284 100644 --- a/tmp/winners.csv +++ b/tmp/winners.csv @@ -24,7 +24,7 @@ Arne "Timwi" Heizmann,Arne_"Timwi"_Heizmann,null,null,timwi@gmx.net,Germany,null Baruch Nissenbaum,Baruch_Nissenbaum,null,null,baruch@eng.tau.ac.il,null,null); Bas de Bakker,Bas_de_Bakker,null,null,bas@bbwt.demon.nl,null,null); Ben Lynn,Ben_Lynn,https://crypto.stanford.edu/~blynn/,null,benlynn@gmail.com,null,@bmxlynn); -Bernd Meyer,Bernd_Meyer,http://byron.csse.monash.edu.au/,null,bmeyer@cs.monash.edu.au,null,null); +Bernd Meyer,Bernd_Meyer,https://web.archive.org/web/20030212213342/http://byron.csse.monash.edu.au/realindex.html,null,bmeyer@cs.monash.edu.au,null,null); Brent Burley,Brent_Burley,null,null,brent.burley@disney.com,null,null); Brian Westley,Brian_Westley,http://www.westley.org,null,brian@westley.org,null,null); Bruce Holloway,Bruce_Holloway,null,null,null,null,null); diff --git a/winners.html b/winners.html index 9e14cf7f3..934dc2793 100644 --- a/winners.html +++ b/winners.html @@ -837,7 +837,7 @@ Contest
  • Best RFC Obfuscation (1996 rcm)
    -
  • Bernd Meyer -- http://byron.csse.monash.edu.au/ +
  • Bernd Meyer -- https://web.archive.org/web/20030212213342/http://byron.csse.monash.edu.au/realindex.html